1. Field of the Invention
The present invention relates to a honeycomb structure having a high heat resistance. More particularly, the invention relates to a heat resistant honeycomb core having a sandwich structure, which is favorably employable for the manufacture of airplanes, railway vehicles, automobiles, hovercrafts, architectures, aerospace structures (e.g., satellite, and developable solar cell paddles for satellite), etc.
2. Description of Prior Art
There have been heretofore known various honeycomb structures such as a honeycomb core made of metal foil such as aluminum foil as described in Japanese Patent Publication No. 59(1984)-40621, a honeycomb core made of plastic material such as polyethylene, polypropylene, polyvinyl chloride and polyester as described in Japanese Patent Publication No. 59(1984)-32306 and Japanese Patent Provisional Publications No. 60(1985)-190340 and No. 60(1985)-245547, and a honeycomb core made of paper.
However, those known honeycomb cores are insufficient in their lightweight property and/or and heat resistance.
An aromatic polyimide is excellent from the viewpoints of the lightweight property and heat resistance, but a conventionally known aromatic polyimide in the form of sheet or film exhibits minimal flexure-deformation property even under heating at elevated temperatures. Further, no adequate adhesive employable for the preparation of a honeycomb core according to a method comprising extending sheets or films has been known, so that a honeycomb core of aromatic polyimide has been not yet prepared industrially and not used practically.
In view of the demand for a heat-resistant honeycomb structure, the present inventors already invented a new honeycomb structure of aromatic polyimide (see U.S. patent application Ser. No. 290,461, filed on Dec. 27, 1988).